"Father time is telling me it's time to go," he wrote. "I have learned over time that the only constant factor is change. It will happen, and there is nothing we can do to stop it, so smile, hold on, and embrace it for all that it has to offer and hopefully you too will have the ride of your life."

Severn, 54, retires with a 101-19-7 pro MMA record. His last fight was a unanimous decision win over Alex Rozman in April.

A former two-time All-American wrestler at Arizona State University, Severn began his MMA career at UFC 4 on Dec. 16, 1994. Severn won two fights that night only to lose via submission in the finals of the tournament to Royce Gracie. The then 36-year-old Severn would rebound to win UFC 5 in 1995.

Other notable wins for Severn were the Ultimate Ultimate 95 tournament in Dec. 1995 and the UFC superfight championship. In addition to the UFC, Severn fought for PRIDE, WEC, King of the Cage, RINGS, Cage Rage, among many others. In fact, after fighting Kimo Leopoldo to a draw at PRIDE 1, he headlined and won the main event of WEC 1 against Travis Fulton in 2001. He was later inducted into the UFC Hall of Fame in 2005.

Severn wrote that he tried to fight fellow legends Royce Gracie, Ken Shamrock and Mark Coleman in retirement fights, but for one reason or another, those fights didn't materialize

An accomplished pro wrestler, Severn added that he will also retire as a wrestler in 2013. The native of Coldwater, Michigan, wrote that he plans on remaining in the MMA world through training and seminars and he hopes to write a book about his illustrious career in the future.